Featured Image Credit: Jorge Gonzalez via Unsplash
By Eva Gruber
One of the most uniquely familiar scents on the planet might just be the smell of fish. The “fishy” smell is almost entirely unique, and to describe it in any words is challenging. Use that word to describe a smell, and that person will know exactly what you’re talking about. Fishy can also be used as an adjective to describe behaviors or circumstances as “not quite right”. “Fishy” tends to hold a negative connotation, likely because the smell of fish is intensified when they begin to get a bit old, or rotten.
Fresh fish caught straight from the sea tend to carry a bit of the smell with them, but the odor is light and fresh, and not overwhelming. But unless you live right on the coast, have an exceptional fishmonger, or caught the fish yourself, most likely the fish you buy at the supermarket will be a few days old and will start to begin smelling quite strongly.
So what exactly makes up the familiar smell of fish? Well, to complicate matters, fish don’t always smell fishy. Sometimes they do, and other times they smell of things that we might think of as pleasant, such as caramel and peaches. The main component, however, in that distinct fishy smell is a molecule called trimethylamine oxide (TMAO), which is contained in the tissues of most sea creatures. It plays a role in stabilizing proteins and in maintaining homeostatic cellular levels, which is crucial to organisms living in saline environments. Deep-sea creatures have more of it, which is why they smell “fishier”. When fish die and are exposed to oxidative processes of air, the TMAO begins to break apart and becomes stronger and more pungent.
The researcher in Germany, Mohamed Mahmoud at FAU, identified ten other compounds that produced distinct smells in the fish he sampled. Geosmin is a compound that gives the fish a musty smell. 2-methylisoborneol is the culprit in the rotten fish smell.
And to even further complicate matters, farmed fish smell differently from wild fish. This is largely due to the environment in which they are raised. In fish farming, the fish are raised in often-overcrowded ponds where environmental contaminants may enter and which the fish cannot escape from into fresh water. Runoff containing manure and fertilizer may enter the system and infiltrate the fishes tissues. This can and does affect the smell (and taste) of farmed fish.